<template>
  <div>
    <p>请选择你要购买的书籍</p>
    <ul>
      <li v-for="(val, index) in arr" :key="index">
        <span>{{ arr[index].name }}</span>
        <button @click="addshu(index)">买书</button>
      </li>
    </ul>
    <table border="1" width="500" cellspacing="0">
      <tr>
        <th>序号</th>
        <th>书名</th>
        <th>单价</th>
        <th>数量</th>
        <th>合计</th>
      </tr>
      <tr v-for="(val, index) in arr" :key="index">
        <td>{{ index + 1 }}</td>
        <td>{{ arr[index].name }}</td>
        <td>{{ arr[index].price }}</td>
        <td>{{ arr[index].count }}</td>
        <td>{{ arr[index].price * arr[index].count }}</td>
      </tr>
    </table>
    <p>
      总价格为: <span>{{ allprice }}</span>
    </p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      arr: [
        {
          name: "水浒传",
          price: 107,
          count: "0",
        },
        {
          name: "西游记",
          price: 192,
          count: "0",
        },
        {
          name: "三国演义",
          price: 219,
          count: "0",
        },
        {
          name: "红楼梦",
          price: 178,
          count: "0",
        },
      ],
    };
  },
  methods: {
    addshu(index) {
      this.arr[index].count++;
    },
  },
  computed: {
    allprice() {
      // reduce接收一个函数作为累加器，数组中的每个值（从左到右）开始缩减，最终计算为一个值
      return this.arr.reduce((sum, obj) => {
        return (sum += obj["price"] * obj["count"]);
      }, 0);
    },
  },
};
</script>
